Effect of long term integrated nutrient management on groundnut productivity and soil fertility under rainfed semi-arid alfisols of southern India

The effect of integrated nutrient management practices on groundnut (Arachis hypogea) mono-cropping system productivity and soil fertility after 37 years of cropping in an undisturbed site for 1985-2021 is being studied in an Alfisols at Agricultural research station, Anantapur under long term permanent manurial trial. The experiment was conducted on an Alfisols under rainfed conditions in a randomized block design. The nine nutrient management treatments were: control (no manure and fertilizer); 100% recommended dose of NPK (20-40-40 NPK kg ha⁻¹); 50% recommended dose of NPK; groundnut shells @ 4 t ha⁻¹; FYM @ 4 t ha⁻¹; 50% NPK+ groundnut shells @ 4 t ha⁻¹; 50% NPK+ FYM @ 4 t ha⁻¹; 100% NPK+ ZnSO₄ @ 50 kg ha⁻¹ and FYM @ 5 t ha⁻¹. All the treatments were replicated thrice. Plots under 100% NPK followed by 100% NPK + ZnSO₄ @ 50 kg ha⁻¹ maintained higher pod yields (30.1 and 27.5% respectively) than control. However, integrated application of groundnut shells and FYM treatments improved the available nutrient status in soil besides sustaining the pod yields after 37 years of mono-cropping. With the exception of control and 50% NPK treatments, there was a positive nutrient balance of NPK in all integrated nutrient management treatments. The available phosphorus and soil organic carbon (SOC) content buildup was conspicuous among all the INM treatments compared to sole application of chemical fertilizers. Application of groundnut shells either solely or in combination with chemical fertilizers was as effective as or even better than FYM in terms of pod yield and carbon build up.